| 1. |
- Krantz, Philip, 1984, et al.
(författare)
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Investigation of nonlinear effects in Josephson parametric oscillators used in circuit quantum electrodynamics
- 2013
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 15, s. (article nr) 105002-
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally study the behavior of a parametrically pumped nonlinear oscillator, which is based on a superconducting quarter wavelength resonator, and is terminated by a flux-tunable superconducting quantum interference device. We extract parameters for two devices. In particular, we study the effect of the nonlinearities in the system and compare to theory. The Duffing nonlinearity is determined from the probe-power dependent frequency shift of the oscillator, and the nonlinearity related to the parametric flux pumping, is determined from the pump amplitude for the onset of parametric oscillations. Both nonlinearities depend on the parameters of the device and can be tuned in situ by the applied dc flux. We also suggest how to cancel the effect of by adding a small dc flux and a pump tone at twice the pump frequency.
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| 2. |
- Krantz, Philip, 1984, et al.
(författare)
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Single-shot read-out of a superconducting qubit using a Josephson parametric oscillator
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 7:11417
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Tidskriftsartikel (refereegranskat)abstract
- We propose and demonstrate a read-out technique for a superconducting qubit by dispersively coupling it with a Josephson parametric oscillator. We employ a tunable quarter wavelength superconducting resonator and modulate its resonant frequency at twice its value with an amplitude surpassing the threshold for parametric instability. We map the qubit states onto two distinct states of classical parametric oscillation: one oscillating state, with 185±15 photons in the resonator, and one with zero oscillation amplitude. This high contrast obviates a following quantum-limited amplifier. We demonstrate proof-of-principle, singleshot read-out performance, and present an error budget indicating that this method can surpass the fidelity threshold required for quantum computing.
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| 3. |
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| 4. |
- Lundell, Björn, et al.
(författare)
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Effective Strategies for Using Open Source Software and Open Standards in Organizational Contexts : Experiences From the Primary and Secondary Software Sectors
- 2022
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Ingår i: IEEE Software. - : IEEE. - 0740-7459 .- 1937-4194. ; 39:1, s. 84-92
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Tidskriftsartikel (refereegranskat)abstract
- Open source software (OSS) and open standards have become increasingly important for addressing challenges related to lock-in, interoperability and long-term maintenance of systems and associated digital assets. OSS projects operate under different conditions and many projects and organisations consider successful governance and strategic involvement with projects to constitute major challenges. Today, many companies seek to establish work practices which facilitate strategic engagement with OSS projects. Based on findings from collaborative research which draws from rich insights and extensive experiences from practice, the paper presents seven actionable strategies for organisations that seek to leverage long-term involvement with OSS projects.
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| 5. |
- Yan, Fei, et al.
(författare)
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Distinguishing coherent and thermal photon noise in a circuit quantum electrodynamical system
- 2018
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 120:26
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Tidskriftsartikel (refereegranskat)abstract
- In the cavity-QED architecture, photon number fluctuations from residual cavity photons cause qubit dephasing due to the ac Stark effect. These unwanted photons originate from a variety of sources, such as thermal radiation, leftover measurement photons, and cross talk. Using a capacitively shunted flux qubit coupled to a transmission line cavity, we demonstrate a method that identifies and distinguishes coherent and thermal photons based on noise-spectral reconstruction from time-domain spin-locking relaxometry. Using these measurements, we attribute the limiting dephasing source in our system to thermal photons rather than coherent photons. By improving the cryogenic attenuation on lines leading to the cavity, we successfully suppress residual thermal photons and achieve T1-limited spin-echo decay time. The spin-locking noise-spectroscopy technique allows broad frequency access and readily applies to other qubit modalities for identifying general asymmetric nonclassical noise spectra.
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